Try removing your email account from your phone, restart the phone (turn it off and back on) and then add the account again.
If that doesn't help then you may want to check that there is nothing else on the device that is interfering and causing the error. Try checking the device for any malware, viruses, bad apps, etc.
Also, when you did the reset, if you chose the option to keep your personal stuff, then this would not have removed any problems. Should you still get this after checking the device for other things, you may want to then save/backup your personal stuff (photos, contacts, etc. -not apps as you can't back those up) and do a "Hard Reset" of the device. This will wipe everything and then reinstall the original OS and items to the device. That should resolve it.
NOTE: Doing this will clear 'all' the data on your tablet, so it is suggested you not choose this option unless you have to, or aren't worried about losing anything on the device.
Be sure you back up any data you want to keep, to a computer or cloud account, before doing the reset.
To "Hard Reset" the tablet...
1. Make sure that the tablet is actually powered off.
2. Remove your SD card, if there is one in the device.
3. Press the "Power" and the "Volume Up" buttons, together, until you see the start-up logo on the screen.
4. Once you can see the logo, release the buttons and allow the device to enter the "System Recovery Mode".
5. Next use "Volume Down" button to get to the "wipe data/factory reset" option When in recovery mode the "Volume Up" and "Volume Down" buttons are how to can navigate and highlight what option you need.
6. Once you have selected the "wipe data/factory reset", press the "Power" button to select that option.
7. On the following screen, repeatedly press the "Volume Down" button until the "Yes - delete all user data" option is what is selected.
8. Then press the "Power" button to hard reset the tablet.
9. If you took your SD card out in step 2, when the device is up and running again, reinsert the SD card.